align each params
do not use _unknown string directly
[protocolbuffers\helper] add some testcases
[protocolbuffers\descriptorbuilder] remove needless setExtension method
[protocolbuffers\descriptorbuilder] remove needless zval
[protocolbuffers\descriptor_builder] add properties initializer
[protocolbuffers\field_descriptor] add ctor flag
[protocolbuffers\helper] add testcases
editing readme. keep small